Method of sealing pressure vessels against leaks



J. S. BAKER Oct. l0, 1939.

METHOD 0F SEALING PRESSURE VESSELS AGAINST LEAKS Filed April 25, 1937Patented oci. 1o, 1939 UNITED STATES PATENT ,OFF-ICE' METHOD F SEALINGPRESSURE VESSEL AGAINST LEAKS V- John S. Baker, Chicago, Ill., assignerto` Cook c Electric Company, Chicago, lll., a corporation of IllinoisApplication April 23, 1937, Serial No. 138,600

1 Claim.

in pressure vessels, and more particularly to an improved method ofsealing'vessels of this type against minute leaks, due to porosity orthe like, Y

5 that are dxmcuit of detection.

' Certain types of pressure vessels are employed under conditionsrequiring an absolute leak-proof construction if they are to bepractical and com- `mercially useful. A pertinent example is an ex 0pansible and contractible vessel used as a vapor difiicultof detectionand may be so minute that it will failto appear during a "test, However,over a period of time, the loss of pressure, as the result' of a loss ofliquid or gas, will reduce the working range of the vessel and atleetthe stroke to a point of rendering the device impractical and ot littlecommercial value. e

Impact arresters are usually employed under 2.'5 conditions and inlocations where the operation is `unnoticeable, while vapor motors areusually employed where failurefof Ioperation, especially if gradual byundetectable minute losses of pressure, will aiect other operationsdependent upon the vapor'motor, which might cause serious damage beforenoticed.

Accordingly, it is 'an object .of this invention to provide an improvedand novel method for sealing pressure vessels against minute leaks,

due to such causes as porosity of the walls or'the like, which arediilicult of detection and will show their eiects only after the devicevhas been installed and in operation for a period of time.

40 More specifically, the present invention relates to a step in theconstruction of a vessel of this type which will assure positive sealingof any and all porous openings or such minute openings that permitlosses of pressure dilcult to detect, and

particularly those openings which are so minute that leakagetherethrough usually does not occur until high internal pressures obtaininthe vessel.-

According to the s'pecic teachings of this invention, the vessel ischarged with a sealing liqvuid and gas under pressure, and is thensealed. The vessel is thereafter agitated or tumbled, so that thesealing liquid is forced to travel over the 'inner surface of the walls.Wherever a porous condition exists, or minute openings permittingleakage usually under pressure only appear, the

porous-like openings in the walls;

The present invention relates to improvements `sealing liquid is forcedinto these' pores -or minute openings and .solidifles.thereby.eiectively sealingl the wall against any and all leaks.

This method of sealing vessels ofl this type may be adapted as anintermediate or as a iinal step l' in the construction. v,

Other objects .and advantages of the invention w'lll be apparent fromthe following detailed description when taken in connection with theaccompanying drawing forming a part thereof. 10

'In the drawing:

Figure 1 is an illustration of one type of pressure vessel that may betreated by the method herein disclosed for sealing against rrnute. or

Fig. 2 Villustrates this type of pressure vessel when Afinallyconstructed; and f Fig. 3 is a detail sectional view of a portion of theinner wall of this type of pressure vessel.

For the purposes of illustratio'n,l I have shown 20- a single adaptationof the invention to a pressure vessel. It is to be understood at theoutset that this adaptation is merely illustrative of the inventiondisclosed so that those skilled in the art will be readily taught how topractice the 28 invention.

It will-also be understoodthat although I have shown only one type ofpressure vessel, those skilled in the art will be taught from thisillustration how to apply the invention to other types $0' of pressurevessels. Not only may the invention be applied to any type of pressurevessel producing a working stroke that should preferably be keptconstant, but it may be used in connection with pressure vesselsdesigned to maintain prede- 85 termined pressures therein. 1

The device illustrated broadly in the drawing comprises a base I, anouter shell 2, and an inner expansible and contractible wall 3. .Outershell 2 and inner expansible and contractible wall 3 40 are hermeticallysealed at l and 5 respectively to base I to provide a. sealed chamber E.The upper end of expansible and contractible wall 3 may be closed by acap 1.

Inasmuch as the device shown in the drawing 45 is an impact arrester ofthe type disclosed in my copending application, Serial No. 93,221 andilled July 29, 1936, body I is provided with a central y threadedopening ,I6 for receiving the connection attaching the impact arresterto a liquid system. 6I!

'I'he interior of the expansible and contractible wall 3 is placed incommunication with the liquid .system -through pipe 8 extending upwardlyinto this wall and terminating' slightly below plate 1, The de vice incompleted form and ready tor operation is illustrated in Fig. 2. Apredetermined quantity of liquid 3 is introduced into chamber 6 throughport I0 that is finally sealed at Il. Glas under pressure is introducedabove liquid 3. Liquid 3 acting as a yieldable body permits expansion offlexible wall 3A within its safe working limit. In the average dwellingor home, water is generally supplied at a pressure of about 45 poundsper square inch. The hammer or pounding action occurring upon th'eclosing ofthe faucet or valve in the systemis the result of a pressurewave that moves backwardly through the system when the flow of the watercolumn is suddenly arrested. Theoretically, it is said that thispressure wave travels backwardly through the system at the rate ofapproximately 4400 feet per second, and, with a normal water pressure of45 pounds per square 'inch in thesystem, it'may increase to a pressureoi' over 400 pounds per square inch. The rapid rise in pressurenecessitates the quick absorption of energy to prevent' the occurrenceof a hammer action.V This -absorption is effected through the expansionof flexible wall 3 and the compression ,of air above liquid l to producean internal pressure balancing fthe pressure wave. It will be observed,therefore, that this type of lvessel is subjected. to high pressureswhich must be maintained. Liquid 3 serves to limit the amount of airthat-need be placed in chamber 6 to produce this internal pressurecapable of balancing the external pressure wave. A flexible wall of thetype illustrated at 3 may 'expand not more than 25% of its length beforereaching the limit of elasticity of the metal wall. It will be observed,therefore. that it is'essential that leakage of liquid I or the airthereabove in chamber 6 be prevented, if this impact arrester is tofunction properly by absorbing the increased energy through producing aninternal pressure balancing the external pressure wave. Due to highpressures, a porous condition of the wall or a minute leakA in the wallwill cause loss of this liquid Il or air. Water. hammers or impactarresters are employed in locations that are usually not visible, andare often forgotten after instalied 'I'he peculiarity of theiradaptation makes it necessary, therefore, that`they function properlyover a long period of time.

To eliminate a porous condition in the wall of the-vessel that isdilcult to detect'even though the vessel is subjected to careful tests,and also such other minute leaks that are likewise diili-.s` cult todetect and will only show their effects' after the device has beeninstalled and used for some time, I propose to insert before liquid 8and air are placed in chamber 6 and the chamber is sealed, a smallquantity of sealing liquid designated I2 in Fig. 1, and thereafter, toVplace chamber 6 under a predetermined pressure, say by injecting a gasunder pressure through port III andtemporarily sealing port I0 asindicated at- II. The device is then agitated or shaken, so

that sealing liquid I2 will flow over the entire inner surface of bothwalls 2 and 3.

` The pressure of the gas that is injected into chamber. 6' may besufficiently high under given conditions to force the sealing liquid I2into any pores or small minute openings in these walls 2 and 3. Ipropose to employ any suitable sealing mediums, and mention lacquer orshellac as being satisfactory sealing mediums under certain conditionsof use.

It will be understood that the present inven' tion is also directed to amethod of employing ainto contact with air.- Consequently, I proposeemploying a gas that will not aifect this sealing liquid so that when itis injected into chamber 6 it will only serve the purpose of forcing thesealing liquid into any pores or minute openings in walls 2 and 3. Asthe sealing liquid is forced into these pores or minute openings,f itwill gradually' come into contact with the. air outside the vessel andsolidify inthe porous or minute openings.

However, this is not essential to the more specic aspects of the presentinvention because any type of sealing liquid may be used which maymerely form a coating over the inner surface of walls 2 and 3. But, Iprefer to employ a gas of a Apressure that will tend to force thesealing liquid I2 into pores or minute openings in the walls` 2 and 3,so vas to assure a tight and perfect sealof these openings byL meansofthis liquid. Forcing sealing liquid I2 into any pores or minute openiunder pressure may thereafter be injected' and the vessel sealed.

As I have previously explained, impact arresters used in a liquid systemare subjected to high pressures. These high pressures -are rapidlycreatedand must be rapidly absorbed. Quite often upon the release ofpressure in the system, top plate I will be brought rapidly back to itsoriginal position. To eliminate injury to plate I that Vmight be causedby its striking the tip of pipe 8, a resilient or semi-resilientabutment I 5 is formed at the tip of pipe 3. A

From the foregoing description it is apparent that'the method of and`means for sealing walls of pressure vessels against porous or minuteopenings may be applied to any type of pressure vessel and isnotvlimited to the type herein illustrated. I prefer to adopt as anillustration an embodiment of the invention the type of pressure vesselshown herein in order to` show the advantages accruing from use of. theinvention.

I do not wish to be limited to the kind of sealing liquid employed, nordo I wish to 'be limited to the manner in which the sealing liquid formsa protective seal where Aporous or mlnuteopenings exist in thewalls ofthe vessel. Aspre-f viously mentioned, sealing liquid I2 may be employedto form only acoating over the inner sury face of the vessel wall andneed not be used," therefore, in connection with a gas under pressurethat will force this sealing liquid into porous or minute openings.;Y Inthis event, there will be an inner coating formed about-the entireinterior l ofthe vessel.

' Without further elaboration, the foregoing will so fully explain thegist of my invention that others, by applying current knowledge, mayread- Yily adopt the same for use under varying conditions of 'servicewithout eliminating certain fea- Y tures which may properly be' said toconstitute the essential items of novelty involved, which items areintended to be definedand secured/to me by the followingjclaim. f

I claim:

The method of sealingporous or like'lminute';

openings in a pressure vessel having a contractible and expansiblewalladpted to haveits operating movement affected by the internalpressure in the vessel which comprises injecting a. liquid into saidvessel that will form a solidied mass when exposed to latmospl'iere,also injecting into said vessel a. gasunder pressure that will not causes olidication of said'liquid, thereafter causing said liquid to flowover the inner surface of said vessel and to be forced into am porous orlike minute openings in the vessels wall by thev pressure of said gas,and eiecting solidication of the liquid in said porous or like minuteopenings by continuing to force said liquid through said openings untilthe liquid reaches theexteror v

